Energy storage systems (e.g., battery energy storage systems) have become increasingly used to deliver power either as part of standalone energy storage systems or as part of a power generation systems (e.g., a wind farm, solar farm, gas turbine system) with an integrated energy storage system. Energy storage systems can include one or more battery banks or other energy storage devices that can be coupled to the grid via a suitable power converter. In some implementations, an energy storage system can include a plurality of energy storage devices. Each energy storage device can be coupled to a power converter or other component of the energy storage system through a contactor. The contactor can be opened and closed to deliver current to or receive current from the energy storage device.
Direct current (DC) contactors typically used with energy storage systems can be unidirectional contactors designed to accommodate opening with current flowing in one direction. For instance, example contactors can make use of magnets and other components to suppress plasma arcs formed between contactor plates of the contactor as the contactor is opened. When current flows in an opposite direction across the unidirectional contactor, debris can build up between the contactor plates as a result of plasma arcs, leading to shorter life of the contactor.
Energy storage devices need to accommodate current flow both to the energy storage device and from the energy storage device during, for instance, charging and discharging of the energy storage device. As a result, contactor life of unidirectional contactors can become an issue when operating the contactors in the energy storage system. Bidirectional contactors can be used to accommodate opening with current flow in multiple directions. However, the use of bidirectional contactors to can lead to increased expense.